The present invention relates to a method and an apparatus for detection of a moving speed of a mobile terminal in mobile communication.
There has been known a method of detecting a moving speed of the movable terminal at a radio base. In this case, the detection of the moving speed is made with reference to a detected value of a received electric field. This technique is, for example, disclosed in the Japanese laid-open patent publication No. 8-33031. In detail, a radio-wave is emitted from the mobile terminal and then received in the radio base for detection of an input level of the received radio-wave. As described in Japanese laid-open patent publications Nos. 8-33031 and 3-104330, the input level of the received radio-wave is in the fading state due to strain of a transmission line. The moving speed is detected from the result of detection of the received electric field with such intense variation in the following manners.
First, center values of the received electric field levels are calculated for every time durations .DELTA.t which are constant in order to determine short time duration center value Rm. Second, as illustrated in FIG. 1, the determined short time duration center value Rm is compared to a threshold value R in order to count the number of divisions of the threshold value R by the determined short time duration center value Rm. Third, a moving speed is calculated from the above counted number in a unit time T (T &gt;&gt;.DELTA.t).
As the moving speed of the mobile terminal is high, a fading pitch is increased by Doppler-effect whereby the number of division of the threshold value R by the determined short time duration center value Rm is increased. The detection of the moving speed of the mobile terminal is made by utilizing those phenomenons.
If, however, a time division multiple access system is used where the received electric field is inputted in burst state, then the accuracy of detection of the moving speed is deteriorated on the following grounds. In case of frequency division multiple access system, the radiowave received in the base is continuous wave. As illustrated in FIG. 1, the moving speed is measured by detecting the number of division of the threshold value R of the fading pitch for a unit time duration. However, the most of the recent mobile communication systems are the time division multiple access system, wherein the radiowave received in the radio base is in the burst state. In this case, the measurement is possible discontinuously but only between the bursts. This results in drop of probability of the detection of the fading pitches by which the threshold value R is divided whereby the accuracy of detection of the moving speed is deteriorated.
In the above circumstances, it had been required to develop a novel method and an apparatus for detecting a moving speed of a mobile terminal in a mobile communication utilizing time division multiple access system, which is free from the above problems.